GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products, from 2256 UTC on 28 November to 1692 UTC on 30 November [click to play animation]

A series of GCOM-W1AMSR2 swaths during the period from 2256 UTC on 28 November to 1692 UTC on 30 November 2018 (above) showed the global coverage of Total Precipitable Water and Wind Speed products from that polar-orbiting satellite.

Surface analyses from the OPC(below) classified this low pressure system as Hurricane Force at 00 UTC and Storm Force at 06 UTC — however, AMSR2 ocean surface wind speeds were as high as 71 knots west of the surface low, 84.8 knots north of the low and 95.6 knots in the vicinity of the occluded front.

Surface analyses at 00 UTC and 06 UTC [click to enlarge]

Shortly after the overpass of GCOM-W1, additional views of the western portion of this storm were provided by Aqua MODIS and NOAA-20 VIIRS (below). (note: the NOAA-20 VIIRS images are incorrectly labeled as Suomi NPP)

Another overpass of GCOM-W1 about 10 hours later continued to show a broad region of strong post-frontal westerly winds to the south of the storm center (below). During that period, the occluded low continued to deepen from 957 to 952 hPa (surface analyses).

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products at 0532 and 1529 UTC [click to enlarge]

Additional features seen in the AMSR2 Total Precipitable Water and Wind Speed products in other parts of the world included the following:

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products south of Iceland at 0353 UTC on 29 November [click to enlarge]

Due to the frequent overlap of polar-orbiting satellite swaths at high latitudes, some locations can have data coverage from numerous consecutive overpasses. The example below shows the Barents Sea — between 70-80º N latitude — during 7 consecutive swaths from 2256 UTC on 28 November to 0847 UTC on 29 November.

GCOM-W1 AMSR2 Total Precipitable Water and Wind Speed products over the Barents Sea from 2256 UTC on 28 November to 0847 UTC on 29 November [click to enlarge]

After increasingly colder air began moving from eastern Nunavut across Hudson Bay beginning on 06 November (surface analyses), the daily sea ice concentration as derived from GCOM-W1 AMSR2 data (source) began to increase in the northern half of Hudson Bay (above) — especially after 15 November once mid-day (18 UTC) temperatures colder than -20ºF were seen at reporting stations along the northwest coast.

A toggle between Terra MODIS True Color and False Color RGB images on 21 November (below) confirmed that much of the northern half of Hudson Bay contained ice — snow/ice (as well as ice crystal clouds) appear as darker shades of red in the False Color image (in contrast to the cyan shades of supercooled water droplet clouds).

19 November maps of Ice Concentration, Ice Stage and Departure from Normal via the Canadian Ice Service(below) further characterized this ice formation, which was ahead of normal for the central portion of Hudson Bay.

GOES-16 (GOES-East) Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) showed a large region of very dry air within a subtropical ridge over the central North Atlantic Ocean on 16 November 2018. Infrared brightness temperatures were unusually warm (brighter yellow to red enhancement) on all 3 Water Vapor bands, especially along the western edge of the dry air.

A GOES-16 Upper-level Water Vapor image at 1700 UTC (below) showed a swath of NUCAPS sounding availability close to that time. The swath passed directly over the driest air within the subtropical ridge.

GOES-16 Upper-level Water Vapor image at 1700 UTC, with a swath of NUCAPS sounding availability [click to enlarge]

One of the green (high-quality) NUCAPS soundings within the arc of driest air (below) revealed a remarkably dry profile above the trade wind inversion — dewpoint values were -50ºC and colder within the 500-620 hPa layer, and dewpoint depressions were about 50ºC near the 550 hPa level.

NUCAPS sounding profile within the driest air [click to enlarge]

Even though the middle to upper tropozphere was quite dry, note that the Total Precipitale Water (TPW) value calculated from the NUCAPS profile was 0.73 inch — there was still abundant tropical moisture within the marine boundary layer of the warm central Atlantic. The GOES-16 TPW product (below) showed minimum values of 0.6-0.8 inch in the region of driest air on the Water Vapor imagery (1800 UTC comparison). In contrast, TPW values over a large portion of the Lower 48 states were 0.6 inch or less, even in regions that appeared to be “moist” on the Water Vapor imagery.

GOES-16 Upper-level Water Vapor + Total Precipitable Water [click to play animation | MP4]

Blended Total Precipitable Water product, with Upper Air sites plotted in white [click to play animation | MP4]

The NESDIS Blended Total Precipitable Water (TPW) product (above) showed an atmospheric river that was transporting moisture northward from the tropics to south-central Alaska during 11 November – 12 November 2018. TPW values were in excess of 2.0 inches near the leading edge of the moisture plume early in the period.

The corresponding Percent of Normal Blended Total Precipitable Water product (below) indicated that these values of TPW were at or above 200 percent of normal (yellow).

Percent of Normal Blended Total Precipitable Water product, with Upper Air sites plotted in red [click to play animation | MP4]

Using the MIMIC Multi-layer TPW site, you can see how TPW is partitioned within various layers of the atmosphere (below). This TPW product uses microwave data from POES, Metop NOAA-20 and Suomi NPP satellites (description). It’s important to keep in mind that the location and continuity of a plume of TPW (such as an atmospheric river) might not always exactly agree what is seen on geostationary satellite Water Vapor imagery, since water vapor spectral bands usually sense radiation being emitted from levels above where the bulk of TPW is normally found (as discussed here).

MIMIC Multi-layer Total Precipitable Water product on 12 November [click to play animation | MP4]

Anchorage, Alaska rawinsonde data from 00 UTC on 11 November to 00 UTC on 13 November [click to enlarge]

The arrival of this moisture produced heavy rainfall and mixed winter precipitation across the region — Portage Glacier (about 50 miles southeast of Anchorage) received 9.99 inches of rainfall in 48 hours, and Anchorage set a new daily precipitation record on 11 November with 0.89″ (which included 1.0 inch of new snow). A summary of temperature and precipitation reports can be seen here.

A comparison of Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 2157 UTC on 12 November (below) revealed widespread layered clouds across most of south-central Alaska.